1. Field of the Invention
The present invention relates to a columnar spacer applied to liquid crystal display (LCD), and more especially, to a photo spacer for thin film transistor liquid crystal display (TFT-LCD).
2. Background of the Related Art
In general, LCD panels can be divided into two types according to methods of fill liquid crystal molecules: vacuum fill LCD and one drop fill (ODF) LCD. In a vacuum fill LCD, the CF substrate and the TFT substrate are combined together with a sealant, and only a hole is kept. Then, liquid crystal molecules are slowly injected into the space between the CF substrate and the TFT substrate by capillarity action. However, this requires a lot of time and a great amount of liquid crystal molecules. Therefore, the vacuum fill method is usually applied to fill only small panels with liquid crystal molecules. In an ODF LCD, first, a sealant layer is pasted onto the bordering part of the TFT substrate. Then, liquid crystal molecules are dropped on the central part of a pixel region, and the CF substrate and the TFT substrate are affixed. Finally, an ultraviolet beam is utilized to irradiate the sealant for hardening the sealant such that the CF substrate and the TFT substrate are tightly combined together. In comparison with vacuum fill method, ODF method is more effective, and needs fewer liquid crystal molecules. Hence, at present, the ODF method is normally applied to fill large LCD panels with liquid crystal molecules.
In ODF, the supporting provided by photo spacers plays an influence on the filling of liquid crystal molecules. The inefficient supporting may cause the shocking of liquid crystal molecules, and reverse, the excessive supporting may cause vacuum bubble or drop flow for liquid crystal molecules. Accordingly, the photo spacers capable of adequate supporting are an important issue for ODF. The photo spacers of different heights formed by laminating photo-resists are illustrated in a prior art. The photo spacers of various areas attached to elements in array are illustrated in another prior art. The spacers of different heights formed by laser scanning are illustrated in another prior art. The difference in height for the photo spacers on TFT side or CF (color filter) side is illustrated in another prior art. The photo spacers with various diameters are illustrated in another prior art. These prior arts aforementioned would not provide efficient resolutions on appreciate supporting strength and preventing shocking.